Construction technology often employs unitized curtainwall units that are anchored to the building structure. A curtainwall system is a lightweight exterior cladding which is hung on the building structure, usually from floor to floor. It can provide a variety of exterior appearances. Curtainwalls are designed to accommodate structural deflections, control wind-driven rain and air leakage, minimize the effects of solar radiation, and provide for maintenance-free long term performance.
The curtainwall is an external, lightweight, generally non-loadbearing wall that is hung from a frame rather than built up from the ground; the framework it shields is usually of concrete or steel. Curtainwalls may be used with any suitable structure but are typically used in high-rise blocks. Typically light, the use of curtainwalls reduces the forces on the foundations, making the building lighter. Curtainwalls are a form of prefabricated construction and can be installed with relative ease, even at significant heights above the ground. Curtainwalls are frequently produced in a ready-to-install form, and thus can be installed as discrete building units.
One aspect of both the design and the installation of a curtainwall is its anchorage to the building structure. Generally, the curtainwall units are anchored to concrete floor slabs, columns and/or shear wall of building structures. Many types of anchor and a variety of methods are used.
Prior art attachment mechanisms for anchoring the curtainwall units to the building structure generally comprise manufactured plates, channel struts, and drilled anchor bolts. Strut type embeds are used in attachment to the face of slab, to columns, or to shear walls. The distance from the building frame face (slab, shear wall, or column) to the back of the curtainwall is desired at approximately at least 2.5 times the specified allowable concrete tolerance plus the bridging clips thickness. Embedded strut type embeds typically have limited, preset depth and thus have no capability for in/out adjustment perpendicular to the plane of the frame to absorb tolerance. Thus, strut type embeds have lateral adjustment only in the plane of the slab, column, or shear wall. In order to effect in/out adjustment, complex two-part primary bridging clips plus ancillary parts are used and must be bolted or welded together to form an assembly. The assembly is then bolted to the strut embed. Protrusions such as the protrusion of the assembly from the strut embed may encroach on the in/out tolerance desired with the distance from the building frame. Further, the two-part bridging clips used for strut type embeds generally interfere and or extend into the plane of the backside of the curtainwall units.
FIGS. 1-3 illustrate prior art anchor systems for attaching a curtain wall to a building frame. FIGS. 1 and 2 illustrate a face of slab anchor system 100. FIG. 3 illustrates a top of slab anchor system 102. As shown, the face of slab anchor system 100 comprises an embed anchor 104, an adjustment piece 106, and an attached piece 110. The embed anchor 104 extends a preset amount into the slab 112. In/out adjustability is provided by the adjustment piece 106. The adjustment piece 106 extends from the face of the slab 112 and thus encroaches on the in/out tolerance of the distance of the attached piece 110 to the slab 112. The attached piece 110 is coupled to the adjustment piece 106.
The top of slab anchor system 102 of FIG. 3 illustrates an embed anchor 114, an adjustment and attachment piece 116, and an attached piece 118. The embed anchor 114 is anchored in the top of the slab 112. The adjustment and attachment piece 116 extends towards the face of the slab 112. The amount of extension of the adjustment and attachment piece 116 determines whether the adjustment and attachment piece 116 is flush with the face of the slab 112 or extends beyond the face of the slab 112. The attached piece 118 is coupled to the adjustment and attachment piece 116. This coupling may be achieved directly or indirectly.
In the past, it has been desirable to locate an anchor in an easily accessible location on top of the floor slab because, while a location on the slab edge, or on the outward facing surface of the frame, is feasible, drilling and welding on the slab edge is more difficult and there is les room for adjustment to accommodate building frame variations. Curtainwall units must be anchored and fixed to a precise theoretical location in space irrespective to the frame's finished location. The difference between the two locations is referred to as tolerance. To bridge the difference in these locations, manufactured parts known as adjustable anchor clips (or adjustable secondary bridging clips) are employed. The clips are typically made utilizing slotted holes, shims or field welding to make the connection between the point of attachment on a building structure and a curtainwall unit.